He told members of the European Parliament he was “disappointed” the US had so far failed to address fears adequately about how passenger information might be used.

Bolkestein will hold further talks with Asa Hutchinson, deputy secretary at the US Department of Homeland Security, on 22 September in Brussels, with a view to resolving their differences.

The commissioner suggested the fight against terrorism couldn’t justify abuses of passenger privacy. “With the second anniversary of 11 September almost upon us, I want to stress that we stand solidly behind the US in the fight against terrorism. But, clearly, the present situation cannot be allowed to continue.”

Since 5 March this year, law enforcement agencies in America have been able to tap into airline computer systems and check who is flying into and out of the US from Europe.

It means the US authorities are able to collect information about passengers, ranging from their credit card details to their address and date of birth. If European carriers fail to grant access to data, they face fines of as much as €5,400 per passenger and the loss of US landing rights.

Bolkestein said that following pressure from Europe, the US had now agreed to delete “sensitive” data such as ethnic background, trade union membership and dietary needs.

But, addressing the European Parliament’s citizens’ rights committee on 9 September, he said that several concerns remained, including the length of time data can be retained (currently 6-7 years) and the scope of information requested by the US authorities.

Another problem, he said, is the purpose for which passenger information can be used. “The US does not want to limit this for the fight against terrorism but to extend it to cover other serious criminal offences,” he said.

The commissioner deplored the fact that concerns about “minimum levels of passenger protection” have not been met. As the Commission “finds it difficult to accept” the present shortcomings, Bolkestein did not rule out stopping the transfer of data altogether. However, this would be up to EU member states to decide.

UK Liberal MEP Sarah Ludford warned that there was a “transatlantic gulf” on the issue and the US was in danger of provoking anti-American feelings in Europe.

A spokesman for the US Mission to the EU said: “We look forward to Department of Homeland Security UnderSecretary Asa Hutchinson’s 22 September visit to Brussels to continue discussions on how to strengthen the security of the travelling public on both sides of the Atlantic.”